Pneumatic motor



Sept. 3, 1946. E. w. DAVIS PNEUMATIC MOTOR 2 Sheets-Sheet 1 Filed Ju ne15, 1945 S p 1946- E. w.'DAv| s 2,406,747

- PNEUMATIC MOTOR Filed June 15, 1945 2 Sheets-Sheet 2 96 7,3 A 82 v I 4I -70 88 v al Patented Sept. 3, 1946 UNITED STATES PATENT OFFICE2,406,747 PNEUMATIC MOTOR Ernest W. Davis, River Forest, Ill.Application June 15, 1945, Serial'No. '599,664

- 1 7 My invention relates generally to pneumatic motors, and moreparticularly to improved valve mechanisms therefor.

It is an object of my invention to provide an" 4 Claims. (Cl. 121-164)Fig. 1 is a central vertical sectional view of the improved lubricantcompressor and pneumatic motor;

Fig.- 2 is a plan view thereof:

Fig. 3 is an enlarged fragmentary sectional view of the valve mechanism,showing the positions of the valves during the downstroke of the motorpiston; and

Fig. 4 is a similar view showing the positions of the valves on theupstroke of the piston.

Referring to Fig. 1, the airmotor is illustrated as forming a part of alubricant pumping mechanism customarily termed a barrel pump, since itis adaptedto remove oils and greases from barrels and drums in which thelubricants and similar products are shipped. This compressor is shown ascomprising a cylinder I6 which is secured to a cover I2 of an oil drumM, the

cylinder l0 extending to the bottom of the drum and having inlet portsl6 normally closed by a foot valve I 8. A piston is reciprocal in thecylinder l0 and is secured to a piston rod 22. Ports 24 in the piston 26are adapted to be closed on the upstroke of the piston by a check valve26. The piston rod extends through a head 28 at the upper end of thebarrel Ill, a suitable pa ki 'gl 30 being provided. The lubricant isdischarged from the barrel l6 through a pipe 32.

A motor cylinder body 34 is preferably cast integrally with pedestals 36which have foot pertions 38 clamped to the end of the barrel ID by capscrews 40, which also secure the head 28 to the'end of the barrel. Avalve actuating arm 42 is clamped against a shoulder 44 formed on thepiston rod 22 by a. sleeve 46. Against the upper end of the latter thereis clamped apiston 48, the-clamping being effected by a nut 50 threadedat the upper end of therod 22.

A cylinder head 52 is suitably secured to the upper end of the cylinderbody casting 34, this head being provided with a passageway 54 leadingfrom a lower valve chamber 56 to the upper end of the cylinder bore 58.The head 52 also has a passageway 60 leading from an upper valve chamber62 to the lower end of the cylinder bore 56 through a connectingpassageway 64 formed in the pump body casting 34.

The bod casting 34 has a sidewardly extending flange portion 66 providedwith a valve seat 68. A second valve seat 10 is formed between the lowervalve chamber 56 and upper valve chamber 62. The upper valve chamber isthreaded to receive a cylindrical bushing 12.

The valve assembly comprises a poppet type valve 14, for cooperationwith the valve seat 68, and a secondpoppet valve 16, for cooperationwith the valve seat 'Hl.v The valve 14 is preferably formed integrallywith a valve stem 86,

while the poppet valve 16 is clamped against a shoulder on the valvestem 86 by a sleeve 82 threaded on the upper end of the stem 80. A 1

cup leather piston 84 is slidable in the bore of the cylinder bushing 12and is clamped between the sleeve 62 and nuts 86 threaded on the upperend Of the valve stem 80.

The valve stem is guided for longitudinal sliding movement in a bushedboss 88 forming part of the pump body casting 34. The lower end portion90 of the stem 80 is of reduced diam eter and has a pair of helicalsprings 92, 93 held thereon, the spring 92 operating to transmit forcefrom the arm 42 to an adjustable stop 94 on the valve stem, while thespring 93is adapted to transmit force from the arm 42 to an adjustablestop 96.

The operating fluid is supplied to the upper valve chamber 62 through aninlet pipe 98 provided with a shutoif valve I66.

In using the apparatus, the operating fluid, such as compressed air, issupplied to the upper valve chamber 62 upon openin the shutoff valveI00. Assuming that the valve assembly and piston 48 are in the positionsshown in Fig. 1, the air under pressure will flow past the poppet valve62 into the lower valve chamber 56, which is always in communicationwith the upper end of the cylinder 58. Thus air under pressure will besupplied to both the upper and lower ends of the cylinder 53, since itis clear that the lower end of this cylinder is at all times incommunication with the upper valve chamber. However, due to the factthat the sleeve 46 is of substantial cross sectional area, it will beapparent that the effec- O tive area of the upper surface of the piston48 is much greater than that of its lower surface, and therefore thepiston 48 will be moved downwardly under the influence of the differencebetween the forces applied to its upper and lower surfaces by thecompressed air. Upon downward movement of the piston 48, lubricantcontained within the lower end of the barrel II) will flow through theports 24 of the piston 20, raising the check valve 26, and some ofthembricant will be discharged through the pipe 32, due to itsdisplacement by the portion of the piston rod 22 which enters the barrelI0. When the piston 48 approaches the end of its downstroke, the arm 42will engage the spring 93 and compress the latter until suificient forceis applied to the valve stem 80, 90, to snapthe valve assembly from theposition in which it is shownin Figs. 1 and 3 to the position in whichit is shown in Fig. 4.

It will be noted that when the valveis in the position of Figs. 1 and 3,the pressure of the operating fluid is exerted'on the balancing cupleather piston 84' as well as over theefiective area of the valve 14.However, because the diameter of the piston 84 isgreater than that ofthe valve 14, the operating fluid will apply a net force to the valveassembly inan upwarddirection.tohold it inthe position in which it .isshown in Figs. 1 and 3. However, as the spring v93 becomes compressedfurther toward the endof the downstroke of the motor piston 43, theforce of the compressed air holding .the .valve assemblyin its upp r.position will be overcome; As soon as the valve 14 leaves its seat, the,pressure inthe lower valve chamber 5 6 will drop and the force ofthecompressed air acting Qntopoi the poppet valve it, as well as theforce, of the compressed spring. 93, will be effective rapidly to snapthe valve assembly from the position shown in Figs. 1 and 3, to theposition shown in Fig. 4.

Whenthe valve mechanism is in the position shown in Fig. 4, air underpressure flows from the upper valve chamber 62 through the passageway6,0, 6 4, to the lower end of. cylinder. 58. thesame time, the air inthe upper end of the cylinder 58 is free to escape tolthe atmospherethrough passageway .54, loWer. valve chamber 56, andthrough the port atthe valve seat 68.

It will be noted that the effective area of the poppet valve 16 and ofits seat. 10 is slightly greater than that of. the bore in the cylinderbushing 12, andthus the air will exertv a net. downward pressure onthevalve assembly. This pressurewill be su flicient to holdthevalveassembly.

in the position in which it is shown in Fig. 4. Thus the motor piston 48will be moved upwardly. During the upward stroke, the lubricant pumpvalve 26 closes and the lubricant above'the piston 2|] is dischargedthrough the pipe 32. Also durll'lg this upward stroke, the foot valve 16opens to admit lubricant. As the piston 48 reaches the upper end ofv itsstroke, the spring 92 is brought into-engagementwith the adjustable stop94 and c mpressed until it applies sufiicient force to the valyestem89,90, to move thelatter to its upper position, as shown in Figs. 1 and3, thus completing a cycle of operation,

Due to the fact that the valves 14 and 16 are of the poppet type, anddue to the use of the cup leather piston 84, the valve mechanism neednot be manufactured with a very high degree of precision, and due to thesuccessive decreases in diameter; of the valve seat 1! the bore of the,

linder ushin andthe v lveseat 68.110. de-,

tent means are required to hold the valve in its two operatingpositions. The dimensions of the latter parts are such that the valvewill not move accidentally due to vibration, and yet sufficient force isapplied to hold the valve assembly in its two operative positions sothat the valve will operate with a snap action.

Whilel have shown and described a preferred embodiment of my invention,it will be apparent that numerous variations and modifications thereofmay be made without departing from the underlying principles of theinvention, I therefore desire, by the following claims, to includewithin the scope of the invention, all such variations and modificationsb which substantially the results of my invention may be obtainedthrough the use of substantially the same or equivalent means.

I claim:

1. In a fluid pressure operated motor, the combination of a motorcylinder, a motor piston reciprocable therein, a piston rod ofsubstantial effective cross sectional area with respect to that of thepiston, and valve means forcontrolling the supply of fluid to theopposite ,ends of said cylinder, said valve means comprising twochambers respectively in communication with opposite ends of saidcylinder, a first valve seat providing a relatively small diameteroutlet port, leading from the first of said chambers to the atmosphere,a second valve seat intermediate said valve chambers, the other of saidchambers having a cylindrical bore open to the atmosphere, said borebeing of slightly less cross sectional area than said second valve seat,and being of substantially greater cross sectional area than said firstvalve seat, a valve assembly having poppet valves respectivelycoo-perable with said valve seats andv having a piston reciprocable insaid cylindrical bore, and means operated by said motor piston to movesaid valve assembly in the direction of piston movement near the end ofeach stroke of the motor piston.

21A valve mechanism for fluid operated reciprocating piston and cylindertype motors comprising, means forming a pair of valve chamberscommunicating with the opposite ends of the motor cylinder, having afirst valve seat inter,-

med-iate the chambers, a balancing piston having one side thereoiexposed to pressure in one of said valve chambers and having its otherside exposed to atmospheric pressure, a second valveseat forming' an airoutlet port leading from the other of said'valvechambersto theatmosphere, a second. valve rigidly connected: to said first valve andto,

saidpiston and cooperable with said second valve seat, said valvesoperating in opposite directions.

otheris fully opened.

3."In a valve mechanism for a fluid operated motor having acylinder andapiston reciprocable therein, a valve. body providing a first chamber anda second chamber, means; connecting the first and spaced so that whenone valve is closed the.

chamber to a source of fluid under pressure means respectivelyconnecting said chambers tov the opposite endsof the motor cylinder, thefirst of said chambers having a cylindrical bore leading to theatmosphere at. one side and a valve seat of greater diameter than saidcylindrical.- bore at. the other side, said second valve 'cham,. herhaving an outlet port, of smaller diameter. than said cylindrical boreleadingv therefrom to he at os er a va ve ass mb y m rising a. pistonmember slidable in the cylindrical bore,.a. p p t valve 00p ae;with..tne yalve.s. at, .and-

a second poppet valve for closing the outlet port, said poppet valvesclosing upon moving the valve assembly in opposite direction and beingspaced apart so that when one valve is closed the other is opened, andmeans for reciprocating said valve assembly in response to movement ofthe motor piston near the ends of its forward and return strokes. v

4. In a valve mechanism for a fluid operated motor having a cylinder anda piston reciprocable therein; a valve body providing a first chamberand a second chamber; means connecting the first chamber to a source offluid under pressure; means respectively connecting said chambers to theopposite ends of the motor cylinder; the first of said chambers having acylindrical bore leading to the atmosphere at one side and a valve seatof greater diameter than said cylindrical bore at 6 the other side; saidsecond valve chamber having an outlet port of smaller diameter than saidcylindrical bore leading therefrom to the atmosphere; a valve asssemblycomprising a piston member slidable in the cylindrical bore; a poppetvalve 00- operable with the valve seat, and a, valve stem secured tosaid piston member and said poppet valve, said valve stem having formedthereon a second poppet valve for closing the outlet port, said poppetvalves alternately closing upon moving the valve assembly in oppositedirection and being spaced apart so that when one valve is closed theother is opened; and means for reciprocating said valve assembly inresponse to movement of the motor piston near the ends of its forwardstrokes.

ERNEST W, DAVIS.

